Holography is a technology of recording and reproducing a real three-dimensional image of an object by means of interference and diffraction principles.
A conventional holographic imaging method is to produce holographic images using the principle of laser interference. Light emitted by a laser source is divided into two beams, one of which irradiates directly towards a photosensitive film and the other of which is reflected by an object to be shot before irradiating towards the photosensitive film. The two beams of light are superimposed on the photosensitive film to produce interference. Finally, the reproduced hologram is further processed according to the basic principle of digital images to remove digital interference, thereby obtaining a clear holographic image. This method has the disadvantages of strict monochromatic requirement and great difficulty in realization of color imaging.
Existing holographic imaging technologies are generally classified into the following three types.
The first type depends on virtual reality or augmented reality glasses or helmet, such as Microsoft's HoloLens, etc. This type of technology has limited application scenarios and currently high costs, due to a need for dependence on auxiliary instrument.
The second type, in dependence on a reflector in high-speed rotation and a projector with high-speed refreshing, is projecting an image on the reflector in high-speed rotation so as to realize a three-dimensional image. The patent document CN105372926A discloses a rotary holographic projection display cabinet utilizing such technology. This technology can hardly achieve interaction, and has very harsh requirements for space.
The third type, in dependence on medium containing fine particles, such as air comprising water vapor, is projecting an image on small water droplets formed by liquefaction of the water vapor. Due to molecular vibration disparity, an image with a strong sense of hierarchy and stereoscopic vision can be formed. The patent documents CN104977794A and CN103116422A disclose application of such technology, both using a water vapor curtain wall to form an image in the air. Application of such technology still involves a need to be equipped with auxiliary tools, for the production of a water vapor curtain wall. Thus, it is not quite convenient to use the third type of technology.
In general, the above technologies, which are imaging in virtual reality or augmented reality tools, imaging in a reflector in high-speed rotation, or imaging in vapor particles in the air, is not imaging in the air in a true sense.